OBJECTIVE: Application of ultrastructural techniques in the search for viruses or viral structural markers in human neoplasms, including leukemia, lymphoma, lymphosarcoma, sarcomas of various types, and carcinomas of various types, including prostatic carcinoma. Elucidation of important ultrastructural features of these tumor cells, both from primary tissue and after growth in tissue culture, is a further goal. APPROACH: Conventional electron microscopy of ultra-thin sectioned material is employed in an in-depth study of tissues of the described human tumors and in cells derived from these tumors and grown in tissue culture. The presence and morphological type of any virus particles is a primary emphasis, as is the detection of any new or unusual ultra-structural feature of any of the tumors. Analysis of tissue culture cells for presence and type of virus particles, freedom from contaminants such as mycoplasma, and detection of identifying ultrastructural features of tissue culture cells is employed as an important adjunct to other types of studies described in other registered projects.